Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 302317
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
717 PM EDT THU OCT 30 2014

.SYNOPSIS...
HIGH PRESSURE WILL WEAKEN OVER THE AREA THROUGH FRIDAY. A STRONG
COLD FRONT WILL SWEEP THROUGH THE REGION FRIDAY NIGHT...FOLLOWED
BY ANOTHER HIGH PRESSURE BUILDING FROM THE WEST OVER THE WEEKEND.
THE HIGH WILL SETTLE ALONG THE SOUTHEAST COAST EARLY NEXT
WEEK...BEFORE SHIFTING OFFSHORE DURING THE MIDDLE OF NEXT WEEK AS
ANOTHER COLD FRONT APPROACHES.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
QUITE A CHANGE IN AIR MASS FROM THIS TIME YESTERDAY...WITH MORE
TYPICAL LATE OCTOBER WEATHER NOW IN PLACE.

A NEARLY STATIONARY FRONT OFF THE SE COAST WILL OSCILLATE AND
EVENTUALLY SHIFT EAST OVERNIGHT AS A FAIRLY PROMINENT SHORT WAVE
ALOFT ARRIVES FROM THE WEST AND CAUSES A SURFACE WAVE TO DEVELOP
ALONG THE FRONT NEAR OR EAST OF THE GULF STREAM WATERS. THE BEST
FORCING AND BETTER HEIGHT FALLS LOOK TO OCCUR IN THE ATLANTIC...SO
FOR NOW WE HAVE MAINTAINED A RAIN-FREE FORECAST OVER LAND.
HOWEVER...GIVEN ISENTROPIC ASCENT ON THE 295K SURFACE AND SOME
BACKING OF THE TRAJECTORIES TO THE SW IN THE MID LEVELS WE
CERTAINLY NEED TO MAINTAIN A SHARP EYE ON RADAR TRENDS AS THERE
WILL BE TIGHT GRADIENT FROM WHERE IT RAINS TO WHERE IT DOESN/T.
AND WE MAY NEED TO CONSIDER AT LEAST SMALL POPS OVER THE COASTAL
ZONES IN FUTURE UPDATES.

OTHER GRADIENTS THAT WILL BE MOST NOTABLE INCLUDE THE SKY COVER
AND TEMP GRIDS. SKIES WILL RANGE FROM CLEAR OR MOSTLY CLEAR FAR
INLAND...PARTLY CLOUDY CENTRAL ZONES...AND PARTLY-MOSTLY CLOUDY
EXTREME EAST. TEMPS WILL BE SIMILARLY DELINEATED...RANGING FROM
MID AND UPPER 40S WELL INLAND TO THE MID AND UPPER 50S ALONG THE
COAST.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
FRIDAY...A SHARPENING UPPER LEVEL TROUGH TAKES SHAPE OVER THE
EASTERN 1/3 OF THE COUNTRY...WHICH WILL SET THE STAGE FOR THE
COLDEST AIR OF THE SEASON FOR THE WEEKEND AND EARLY NEXT WEEK. THE
REGION WILL BE BETWEEN A WEAK WAVE OF LOW PRESSURE MOVING AWAY TO
THE NORTHEAST OVER THE ATLANTIC AND AN UPPER SHORTWAVE IN THE BASE
OF THE LARGER TROUGH MOVING TOWARD THE AREA FROM THE NORTHWEST.
EXPECT MOST OF FRIDAY TO BE DRY BETWEEN THESE SYSTEMS...BUT CLOUDS
WILL BE ON THE INCREASE BY AFTERNOON AS THE UPPER TROUGH MOVES INTO
THE AREA. IT WILL BE THE WARMEST DAY OF THE PERIOD BEFORE THE BIG
COOL DOWN...WITH HIGHS NEAR NORMAL IN THE LOWER 70S. BY FRIDAY
NIGHT...A STRONG UPPER TROUGH DIGS SOUTHWARD...REACHING JUST NORTH
OF THE AREA BY SUNRISE. MOST OF THE MOISTURE SKIRTS ACROSS THE
NORTHERN 1/3 OF THE AREA. HAVE KEPT SLIGHT CHANCE POPS FOR
SHOWERS. THE LEADING EDGE OF THE STRONG POLAR FRONT WILL BE JUST
REACHING THE COAST BY SUNRISE. THUS...LOWS WILL BE COOLER...BUT NOT
AS COLD AS THE NEXT FEW NIGHTS...IN THE LOWER TO MID 40S.

SATURDAY...A VERY COOL AND BLUSTERY DAY IS EXPECTED. THE STRONG
UPPER TROUGH MOVES ACROSS THE NORTHERN FORECAST AREA...WHICH IS
WHERE THE BEST DEEP LAYER MOISTURE WILL ALSO RESIDE. EXPECT
SCATTERED SHOWERS ACROSS THE NORTHERN 1/3 OF THE AREA UNDER THE
UPPER LOW. MODEL SOUNDINGS STILL SUPPORT THE CHANCE FOR SOME FROZEN
PRECIP/GRAUPEL...BUT NO ACCUMULATIONS EXPECTED...AND OVERALL LIQUID
QPF AMOUNTS EXPECTED TO BE MAINLY 0.2 INCHES OR LESS. HIGHS WILL
STRUGGLE TO GET OUT OF THE LOWER 50S...AND WOULD NOT BE SURPRISED IF
THEY HELD AROUND 50 IF THE CLOUDS ARE THICK ENOUGH WITH STRONG COLD
ADVECTION. WINDS WILL BE VERY BREEZY...WITH 15-25 MPH SUSTAINED AND
GUSTS 30 TO 35 MPH. SATURDAY NIGHT...A STRONG SURFACE RIDGE BUILDS
FROM THE NORTHWEST...AND WITH CLEARING SKIES AND WEAKENING PRESSURE
GRADIENT...WILL ALLOW WINDS TO GRADUALLY DROP OFF. STILL EXPECT SOME
LIGHT WINDS OF 5 TO 10 MPH MOST OF NIGHT...BUT WILL DROP TO VERY
LIGHT WELL INLAND. LOWS WILL BE QUITE COLD...IN THE MID TO UPPER
30S...EXCEPT LOWER TO MID 40S COAST. COULD BE SOME PATCHY FROST WELL
INLAND ACROSS WIND PROTECTED AREAS.

SUNDAY...THE SURFACE RIDGE BUILDS RIGHT OVER THE REGION AS THE UPPER
RIDGE AXIS BUILDS OVER THE MID ATLANTIC AND SOUTHEAST. STILL EXPECT
COOL MAX TEMPERATURES...ONLY IN THE UPPER 50S TO AROUND 60 UNDER
MOSTLY SUNNY SKIES. BY SUNDAY NIGHT...PROBABLY THE COLDEST
TEMPERATURES OF THE SEASON AS THE SURFACE RIDGE IS NEARLY PERFECTLY
POSITIONED OVER THE REGION FOR IDEAL RADIATIONAL COOLING UNDER CLEAR
SKIES. EXPECT LOWS IN THE LOWER TO MID 30S MOST INLAND AREAS. RIGHT
NOW...CHANCES FOR WIDESPREAD FROST SEEM TO BE INCREASING GIVEN
SURFACE DEW POINT TEMPERATURES SHOWN BY GUIDANCE TO BE 30 TO 32 DEGS.

LAKE WINDS...A STRONG COLD FRONT WILL MOVE ACROSS THE AREA BY EARLY
SATURDAY...WHICH IS EXPECTED TO PRODUCE STRONG WINDS OF 20 TO 25 KT
AND GUSTS AROUND 30. STRONG WINDS AND ROUGH WAVES WILL LIKELY
PERSIST INTO THE FIRST PART OF SATURDAY NIGHT BEFORE SUBSIDING.  A
LAKE WIND ADVISORY IS EXPECTED TO BE ISSUED WITH LATER FORECASTS.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
MEDIUM RANGE GUIDANCE IS IN GOOD AGREEMENT WITH THE GENERAL SYNOPTIC
PATTERN THROUGH THE LONG TERM PERIOD. IN THE MID AND UPPER LEVELS OF
THE ATMOSPHERE...A STRONG RIDGE WILL SHIFT EASTWARD AND EXPAND OVER
THE REGION EARLY NEXT WEEK...BEFORE SHIFTING INTO THE ATLANTIC AS A
TROUGH APPROACHES FROM THE WEST DURING THE MIDDLE OF THE WEEK.
MEANWHILE AT THE SURFACE...STRONG HIGH PRESSURE WILL SETTLE ALONG
THE SOUTHEAST COAST EARLY NEXT WEEK THEN SHIFT INTO THE ATLANTIC BY
MID-WEEK...WITH A COASTAL TROUGH POSSIBLY DEVELOPING WEDNESDAY
BEFORE A COLD FRONT MOVES THROUGH THURSDAY.

OVERALL...THIS PATTERN WILL FAVOR RAIN-FREE CONDITIONS EARLY IN THE
WEEK...WITH A SLIGHT CHANCE FOR SHOWERS WEDNESDAY WITH THE COASTAL
TROUGH/ONSHORE FLOW AND THURSDAY WITH THE COLD FRONT. PATCHY FROST
COULD OCCUR INLAND FROM THE COAST SUNDAY NIGHT...WITH SOME FREEZING
TEMPERATURES POSSIBLE IN WELL SHELTERED LOCATIONS AS WELL.
THEN...TEMPERATURES WILL MODERATE THROUGH THE REMAINDER OF THE LONG
TERM PERIOD RETURNING TO NEAR OR SLIGHTLY ABOVE NORMAL BY THE MIDDLE
OF NEXT WEEK.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
MVFR CEILINGS WILL ATTEMPT TO ADVECT INTO OR FORM OVER THE
TERMINALS LATER TONIGHT INTO FRIDAY MORNING IN RESPONSE TO A
DEVELOPING AREA OF LOW PRESSURE IN THE ATLANTIC. FOR NOW THOUGH WE
ARE CONTINUING WITH A VFR FORECAST THROUGH 00Z SATURDAY WITH NO
CLEAR INDICATORS OF HOW FAR WEST THESE LOWER CEILINGS WILL BE FROM
OFF THE OCEAN.

EXTENDED AVIATION OUTLOOK...
A STRONG UPPER TROUGH AND ASSOCIATED SURFACE COLD FRONT WILL MOVE
ACROSS THE AREA LATE FRIDAY NIGHT AND SATURDAY. PERIODS OF MVFR
CONDITIONS POSSIBLE MAINLY FOR KCHS WITH SCATTERED SHOWERS. WINDS
WILL BE QUITE STRONG...WITH WEST- NORTHWEST SUSTAINED 20 TO 25 KT
AND GUSTS AROUND 30 KT POSSIBLE. CONDITIONS EXPECTED TO IMPROVE
LATER SATURDAY NIGHT AND SUNDAY WITH A RETURN TO VFR CONDITIONS
SUNDAY INTO EARLY NEXT WEEK.

&&

.MARINE...
TONIGHT...A STALLED OUT FRONT ALIGNED NORTH/NE TO SOUTH/SW AND OUT
EAST OF THE GULF STREAM WILL CONTINUE THROUGH THE NIGHT...AWAITING
FOR A MID LEVEL IMPULSE/S ENERGY TO SPARK A SURFACE LOW ABOUT 100
MILES OFF THE SC COAST LATE. THIS ALONG WITH AN INCREASE IN COOL
ADVECTION...PLUS A PACKING OF THE GRADIENT WILL ALLOW FOR SOME
HIGHER WINDS TO DEVELOP WITH TIME. WE/LL START THE NIGHT WITH
NORTH/NE WINDS OF 10-17 KT OVER THE ATLANTIC AND 5-10 KT IN
CHARLESTON HARBOR...THEN SLIGHT BACKING WILL TRANSPIRE OVERNIGHT
AS SPEEDS CLIMB UPWARDS TO 13-20 KT IN THE OCEAN LATE AND UP NEAR
10-12 KT IN THE HARBOR. SEAS WILL BEGIN THE NIGHT AT 2-3
FT...BUILDING ABOUT A FOOT OR SO AFTER MIDNIGHT. ISOLATED TO
SCATTERED SHOWERS WILL FORM DURING THE LATE EVENING AND OVERNIGHT
HOURS...WITH MAYBE SOME T-STORMS OUT NEAR THE GULF STREAM WHERE
THE BEST INSTABILITY WILL BE FOUND.

FRIDAY THROUGH TUESDAY...
NO HIGHLIGHTS FRIDAY BUT CONDITIONS WILL GO DOWNHILL FOR LATE FRIDAY
NIGHT AND SATURDAY AS A STRONG COLD FRONT MOVES THROUGH. EXPECT
WINDS TO INCREASE TO GALE CONDITIONS BY VERY LATE FRIDAY NIGHT AND
EARLY SATURDAY MORNING. EXACT TIMING OF THE POTENTIAL GALE
CONDITIONS A LITTLE UNCERTAIN RIGHT NOW...BUT THINK BY AFTER SUNRISE
SATURDAY MOST MARINE AREAS WILL BE EXPERIENCING GALE/NEAR GALE
CONDITIONS...ESPECIALLY WITH WIND GUSTS. THUS...HAVE RAISED A GALE
WATCH FOR THE ATLANTIC WATERS LATE FRIDAY NIGHT THROUGH THE FIRST
PART OF SATURDAY NIGHT. HAVE GONE WITH A SMALL CRAFT ADVISORY FOR
THE HARBOR FOR NOW...BUT MONITORING THE POTENTIAL FOR GALE
CONDITIONS THERE TOO. WINDS AND SEAS WILL GRADUALLY DECREASE LATER
SATURDAY NIGHT AND EARLY SUNDAY...AND SHOULD SEE CONDITIONS FALL
BELOW ANY HIGHLIGHTS BY LATER SUNDAY. HIGH PRESSURE BUILDS OVER THE
WATERS MONDAY AND TUESDAY WITH WINDS 15 KT OR LESS AND SEAS 4 FT OR
LESS.

&&

.CLIMATE...
RECORD LOW MAX TEMPERATURES FOR SAT NOV 1...
KCHS 56 /1993/...
KSAV 52 /1925/...
KCXM 52 /1925/...

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 5 AM EDT SATURDAY TO 7 AM EST SUNDAY
     FOR AMZ330.
     GALE WATCH FROM LATE FRIDAY NIGHT THROUGH LATE SATURDAY NIGHT
     FOR AMZ350-352-354-374.

&&

$$

NEAR TERM...
SHORT TERM...RFM
LONG TERM...JAQ
AVIATION...
MARINE...
CLIMATE...






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